Process for producing potassium hydroxide composition



Patented Aug. 23, 1949 UNITED STAT .EENT

PIC

PROCESS FOR PRUDUGLNG POTASSIUM .HYDROXIDE COMPOSZL'IIION land- NoDrawing. Application June 11, 1945, Serial No. 598,917

6 Claims.

Our invention relates to a novel processior ob,-

taining potassium hydroxide in a finely-divided and highly-active state.More particularly, "it relates to such finely-divided and highly-activepotassium hydroxide in the form of a suspension in a water-immisciblealkyl acetal, and to a method for preparing suchsuspensions by heatingsolid potassium hydroxide or aqueous solutions thereof with an acetal inthe presence or absence of a small proportion of a primary :monohydricaliphatic alcohol containing from four to eight carbon atoms, asdescribed hereinafter.

For carrying out various chemical processes, it is often desirable toutilize potassium hydroxide in a finely-divided state, suspended in acarrying medium. This is particularly true, for example, in thereactions involving the absorption of l-alkynes such as acetylene, inwhich a very large surface area of the potassium hydroxide must bepresent to absorb the acetylene and to convert it into a form suitablefor subsequent reaction with carbonyl compounds to term acetylenicalcohols.

Ordinary mechanical methods for obtaining the potassium hydroxide in thefinely-"divided and highly-active state necessary for this and otherpurposes have presented many difiiculties. Mes chanical grinding of thesolid potassium hydroxide has been difficult and not as efiective-asdesired because the solid potassium hydroxide presents a waxy eiiecttothe'g-rinder and resists comminution. This results in a product thatis too coarse for easy suspension in the carrying liquid, and too coarsefor-most efifeotiveuse in the processes ref erredto.

We have now found that solid potassiumhydroxide can be heated to itsfusion temperature with a Water-immiscible liquid of the typehereinafiter described and subsequently cooled with agitation below itsmelting point to form a slurry of.f1nely-divided solid particles ofhighly reactive-potassium hydroxide in the-water-immiseible liquidCommercial potassium hydroxide U. S. P. pellets containin 10-13% watermay be thus fused: at a temperature around 1-00 C. and hence arelatively low boiling acetal' can be. used. With other gradescontaining lower percentages of water, it is necessary to use higherboiling acetals, or to operate the reactor under pressure, in ordertoeffect' fusion.

We have also found that when a water-unmiscible liquid of the typehereinafter described is added to an aqueous solution of potassimn .hy-

dioxide: and: the mixture distilled with. acoom- 2 panying vigorousagitation, with removal of the water from the distillate and return ofthe waterimmiscibie liquid to the distillation vessel, the free water,as hereinafter defined, can be substantially completely separated fromthe mixture, leaving a two-phase liquid residue which, when agitated andcooled, is converted into a suspension of finely-divided, solidparticles of highly reactive potassium hydroxide in the waterimmiscibleliquid.

The removal of all of the distillable water, as mentioned above, doesnot leave the still residue completely anhydrous. On the contrary, itmay contain up to slightly below one mole of water per mole of potassiumhydroxide, depending on the boiling point and relative concentration ofthe acetal used Ifor carrying out the dehydration. The water, however,does not behave like free water; it "is-apparently combined with thepotass'nzm hydroxide, and does not interfere with the activity of theresidual anhydrous potassium hydroxide. In this connection, theexpression "free" water herein referred to, is to be con strued asmeaning only that Water which may be removed from the above-mentionedmixtures by distiEIl'at-ion with acetals.

The' complete separation of water from the potassium hydroxide solutionis not essential for the preparation of a solid, finely-divided, activeproduct utilizable for the processes described. In fact, the preparationof a strictly anhydrous potassimnhydroxiide would not be practical,since ithasa meltm g point of about 360 C., and would 'bezdifli'cult or"impossible to maintain in fluid condition at the boiling temperatures ofmany of the water immiscible liquids of our invention. The product as itcommonly appears in the so called dry solid state as a commercialmaterial is sufiiciently' dehydrate-:1 for our purposes. This form ofpotassium hydroxide fortunately can be maintained in a liquid conditionat temperatures considerably below the melting point of anhydrouspotassium hydroxide, so that it remains in fluid form at the boilingtemperatures of the various water-immiscible liquids of our invention,some of which boil as low as about C. to C. at atmospheric pressure; andin suchfl'uid condition the potassium hydroxide may readily becomm-muted by the vigorous agitation and cooling employed in ourprocess, and thereby finely dispersed .in the carrying liquidsdescribed. Other liquids which We may use have somewhat higher boilingtemperatures, but as a matter of convenience the majority of the liquidsmost adaptable to our processes will have boiling points from about 100to 250 r 300 C., considerably below the melting point of the anhydrouspotassium hydroxide.

The particular advantages of the potassium hydroxide composition of thepresent invention will be recognized when it is recalled that with priorexisting methods involving the utilization of anhydrous potassiumhydroxide, workers were confronted with the problem of recovering largequantities of that material from aqueous mixtures, dehydrating thepotassium hydroxide, and then pulverizing it for re-use in thesucceeding batch. It will be obvious that this requirement renders suchpractice substantially useless from an industrial point of view, sinceit is not economically feasible to recover large quantities of potassiumhydroxide from aqueous mixtures thereof in an anhydrous condition andthen to grind the materials to a finely-divided powder suitable forre-use.

In accordance with our invention, we utilize hydrous potassiumhydroxide, either as the solid base, preferably the U, S. P. grade whichcontains approximately 12.5 per cent by weight of water, or aqueouspotassium hydroxide of substantially any concentration, although ofcourse, the more concentrated the solution, the more quickly will theWater separation be effected.

The potassium hydroxide or solution thereof, as the case may be, ismixed with the appropriate water-immiscible liquid as describedhereinafter and is subjected to distillation in such a manner that thefree water is removed as a separate layer from the distillate, anddiscarded, while the water-immiscible liquid is continuously'returned tothe distillation vessel. Distillation is continued until no more waterdistills over. The still contents then exist in the form of two liquidphases, one phase comprising the water-immiscible liquid, the other thefluid potassium hydroxide. After the distillation is complete, thecontents of the distillation vessel are allowed to cool, usually down toroom temperature to permit solidification of the potassium hydroxide,and during this cooling stage the vigorous agitation is continued. Theagitation may be effected by any of the convenient known methods, butthe turbulence should be of a magnitude sufiicient to effect fineprecipitation and thorough dispersion of the finely-divided particles.Potassium hydroxide, treated in this manner, presents a greater activesurface than that produced by mechanical means, or by other processesusing different types of dehydrating liquids; hence, a given weight ofsuch potassium hydroxide will produce a greater weight of product in thereactions for which it is adapted.

We obtain our improved finely-divided and highly-active potassiumhydroxide by the use of water-immiscible acetals which function toremove water from mixtures thereof with potassium hydroxide solutions,and which do not react irreversibly with the potassium hydroxide. Suchacetals, it has been observed, have the property of activating potassiumhydroxide for many reactions, the degree of activation being greatlyenhanced by our processing technique. Acetals which are to be utilizedunder atmospheric pressure should preferably possess a boiling point ofat least about 100 C. Lower-boiling acetals can be used, but require theapplication 'of superatmospheric pressures in order to produce thedesired liquid layer of potassium hydroxide. Specific examples ofsuitable acetals are 1,1-dibutoxyethane, 1,1-dimethoxybutane,2-ethyl-2-methyl- 1,3-dioxolane, 1,1-dimethoxy-2-ethylhexane, 1,1-dipropoxybutane, and 1,1-dibutoxybutane.

The finely-divided suspended particles of potassium hydroxide preparedby the use of acetals appear to differ decidedly both in size andphysical structure from the particles of potassium hydroxide obtained byprior processes. They are, for example, somewhat more finely-dividedthan those formed in the hydrocarbons and of a fluffy or leafy characterrather than of a sandy character such as is obtained in hydrocarbons.The physical characteristics of our potassium hydroxide particlesproduce a more enduring type of suspension; and when the particles dosettle somewhat, they settle loosely without compacting, and can readilybe resuspended with gentle stirring.

We have found that the reactivity of the finelydivided potassiumhydroxide obtained by our process may be materially increased byincorporating with the water-immiscible acetal used to remove the waterfrom the potassium hydroxide a small proportion of a primary monohydricaliphatic alcohol containing from four to eight carbon atoms, such asfor example, l-butanol, methylallyl alcohol, l-pentanol, isoamylalcohol, and l-octanol. The proportion of alcohol to acetal may varyconsiderably. However, it has been our general observation thatsatisfactory results are consistently obtained when up to about 35 percent of the alcohol, based on. the total volume of the reactionmenstruurn, is utilized. When, for example, a mixture of an acetal andan alcohol of the above type is used to prepare a finely-dividedsuspension of potassium hydroxide in accordance with our procedure, agrade of potassium hydroxide is obtained which when used in thecondensation of suitable l-alkynes with carbonyl compounds, ordinarilygives both a h gher conversion to acetylenic alcohols and a higheroutput of acetylenic alcohols per unit volume of the reaction menstruum.

Although the potassium hydroxide mixtures of the present inventionabsorb l-alkynes readily, substantially all of the latter are releasedif the solution is then heated, and the residue can again be used forfurther absorption. These potassium hydroxide mixtures will, therefore,be found useful for the removal of l-alkynes of the above-mentionedclass from various gas mixtures.

Our invention may be further illustrated by the examples which follow:

EXAMPLE I Four hundred parts of 1,1-dimethoxy-2-ethylhexane was added toa solutionconsisting of 20 parts of potassium hydroxide dissolved in 30parts of water. The resulting two-phase mixture was heated to refluxtemperature, and the water removed therefrom in the form of anazeotropic mixture with the 1,1-dimethoxy-2-ethylhexane, which; aftersubsequent separation from the water, was returned to the still kettle.Throughout the heating period, and also while cooling, the mixture wasstirred vigorously. The resulting composition consisted of a suspensionof finely-divided potassium hydroxide in 1,1-dimethoxy-Z-ethylhexane.

EXAMPLE II Six hundred milliliters of 1,1-dibutoxyethane was added withagitation to 187 g. of potassium hydroxide U. S. P. pellets. Theresulting mixture was heated to C., with agitation and then cooled to.10 C. with continuous agitation, thus being converted into afinely-divided slurry of solid particles of potassium hydroxide in1,1-dibutoxyethane.

EXAMPLE III A mixture consisting of 558 ml. of 1,1-dibutoxyethane, 42ml. (approximately 7 per cent) of butanol, and 187 g. of potassiumhydroxide U. S. P. pellets containing 13 per cent water, was refiuxedfor fifteen minutes at a liquid temperature of 188 C., during which timetwo liquid layers were formed. The mixture was then cooled to C. withagitation. The resulting composition consisted of a suspension offinely-divided solid particles of potassium hydroxide in1,1-dibutoxyethane and butanol.

A surprising feature of our invention is the discovery that potassiumhydroxide prepared in accordance with our invention using acetals issubstantially more reactive than when prepared with other liquids suchas, for example, hydrocarbons. This is illustrated by the data shown inthe following table, taken from experiments in which potassium hydroxideslurries were first saturated with acetylene and subsequently reactedwith acetone to form 2-methyl-3-butyne- 2-01. Column 1 represents fourdifierent samples of suspensions of potassium hydroxide prepared inexactly the same manner with difierent kinds of water-immiscibleliquids.

X-2 represents a suspension of potassium hydroxide prepared as describedunder Example II above, using as the acetal 1,1-dibutoxyethane.

X-3 represents a similar suspension of potassium hydroxide prepared asdescribed under Example III above, using a mixture of 1,1-dlbutoxyethaneand butanol.

"A represents a sample of potassium hydroxide suspension preparedexactly as described in Example 11 above, with the exception that xylenewas used instead of 1,1-dibutoxyethane.

B represents a suspension of potassium hydroxide prepared exactly asdescribed under Example II above, with the exception that butyl etherwas used instead of 1,1-dibutoxyethane.

Table Conversion of Acetone to 2-Methyl- 3-butyne-2ol MenstruumPotassium Hydroxide Suspension Output Per cent all.

Examination of the data given in the above table shows readily theobvious advantage from the use of potassium hydroxide of the typeprepared by our improved procedure. Improved results of a similarcharacter are obtained when using our improved type of potassiumhydroxide in other chemical processes requiring an activated form ofpotassium hydroxide either as a reactant or as a catalyst. Examples ofsuch uses include the preparation of chloretone, etc.

It will be obvious to those skilled in the art that otherwater-immiscible acetals of the character described, in addition tothose specifically enumerated herein, may be utilized in carrying outour invention, and that the above examples are merely illustrative ofour invention and in no way limit the scope thereof. On the contrary,

it is intended that the present invention shall cover, by theterminology of the appended claims, all features of patentable noveltywhich are inherent therein,

This application is a continuation-in-part of our U. S. Serial No.511,838, filed November 26, 1943, now abandoned.

Having described our invention, what we claim is:

1. A process for producing a highly-active suspension of solid potassiumhydroxide which comprises mixing a hydrous potassium hydroxide with aliquid water-immiscible alkyl acetal having a boiling point within therange of about to 300 C. which does not substantially react irreversiblywith the potassium hydroxide, heating the mixture above the meltingpoint of the hydrous potassium hydroxide and distilling off any waterwhich may be present in excess of about one mole of water per mole ofpotassium hydroxide, then cooling the resulting mixture to a solidifiedpotassium hydroxide while vigorously agitating to produce afinely-divided, highly-active suspension of potassium hydroxide,

2. The process of claim 1 wherein from about 7 to 35 per cent of aprimary monohydric alcohol containing from four to eight carbon atoms ispresent in the mixture.

3. The process of claim 2 wherein said primary monohydric alcohol isbutanol.

4. The process of claim 1 wherein said alkyl acetal is1,1-dibutoxyethane.

5. A process of producing a highly-active suspension of solid potassiumhydroxide which comprises mixing a hydrous potassium hydroxide with aliquid alkyl acetal having a boiling point within the range of about 100to 300 C. which does not substantially react irreversibly with thepotassium hydroxide, distilling the mixture to remove water in the formof the azeotrope with said alkyl acetal, removing the water from thedistillate and returning the latter to the mixture, continuing thedistillation until the water in the mixture is reduced to an amount notsubstantially exceeding one mole per mole of potassium hydroxide, thedistillation being conducted at a temperature sufficiently high to causeat least partial fusion of the potassium hydroxide, cooling the mixturewhile vigorously agitating the same to solidify the potassium hydroxideand to produce a finely-divided, highly-active suspension of the same.

6. The process of claim 5 wherein the mixture contains from about 7 to35 per cent of the primary monohydric alcohol containing from four toeight carbon atoms.

GLEN H, MOREY. EVERET F. SMITH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,835,271 Burke et a1. Dec. 8,1931 2,019,468 Bacon Oct. 29, 1935 2,288,667 Allen et al July 7, 19422,326,099 Kokatnur et al Aug. 3, 1943 2,345,170 Zeltner et a1. Mar. 28,1944 2,367,273 Hall et al Jan. 16, 1945 2,385,548 Smith Sept. 25, 1945

